where \(M\)  is the mass parameter. In order to find the horizons of the above spacetime, we find the points where the timelike Killing vector field becomes null. We solve for \(\left(1-\frac{2M}{r}-\frac{\Lambda r^2}{3}\right)=0\) . This is a cubic equation admitting three roots, for \(0<3M \sqrt{\Lambda } < 1\) , e.g. [1]}, [2]}.
\(r_{H}=\frac{2}{{\sqrt{\Lambda }} }\cos \frac{\pi +\cos ^{-1}(3M\sqrt{\Lambda })}{3},~r_{C}=\frac{2}{{\sqrt{\Lambda }} }\cos \frac{\pi -\cos ^{-1}(3M \sqrt{\Lambda })}{3},~r_{U}=-(r_H+r_C)\) 
